Drag reduction towing system

ABSTRACT

A cylindrical body suitable for towing has a support secured to its surface. The support and cylindrical body have parallel axes with the support extending aft a distance beyond the body. Horizontal and vertical fins of a dimension of 30 percent to 40 percent of the lateral cross-sectional area of the body are secured to the aft end of the support. A drop fin having an area of 20 to 30 percent of the vertical lateral area of the body is affixed to the aft end of the body. An increased separation between the center of gravity and center of pressure is effected by the above plurality of fins.

v "ca 11 242. OR 3,839,985 SR 5 United btates Patent Modert 1451 Oct. 8,1974 v [54] DRAG REDUCTION TOWING SYSTEM 3,749,045 7/1973 Angus 114/235B [75] Inventor: 21:51am F. Modert, New London, Primary Examiner Duane AReger Assistant Examiner-Gregory W. OConnor [73] Assi nee: The UnitedStates of America as Attorney, Agent, or Firm-RichardSSciascia; Arthurrepresented by the Secretary of the A. McGill; Prithvi C. Lall Navy,Washington, DC. 22 Filed: Nov. 14, 1973 [57] \BSTRACT A cylindrical bodysuitable for towmg has a support PP 415,839 secured to its surface. Thesupport and cylindrical body have parallel axes with the supportextending 52 us. c1. 114/235 1: aft adistance beyond the body Horizontaland vertical 51 hi. or B63!) 21/00 fins of a dimension of 30 Permt to 40Permt of the [58] Field of Search 1 14/235 B 23 5 340/3 T lateralcross-sectional area of the body are secured to the aft end of thesupport. A drop fin having an area [56] References Cited of 20 to 30percent of the vertical lateral area of the body is affixed to the aftend of the'body. An in- UNITED PATENTS creased separation between thecenter of gravity and 3,137,264 6/l964 Bramard et a]. 1 14/235 B Centerf pressure i effected by the above plurality of 3,327,968 6/1967Converse ll4/235 B fins 3,53l,76l 9/l967 Tickell et al. 114/235 B3,560,912 2/1971 8 Claims, 3 Drawing Figures Spink et al. [14/235 BSTATEMENT OF GOVERNMENT INTEREST DESCRIPTION OF THE PREFERRED EMBODIMENTMaintaining a proper orientation for a towed object The inventiondescribed herein may b n f 5 is a problem for any towing system. Aproblem that has tured and used by or for the Government of the UnitedStates of America for governmental purposes without the payment of anyroyalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention generally relates tothe towing of objects in water and more particularly to a system forimproving the towing characteristics of towed objects.

The art of towing objects in water probably predates man and all otherland animals, back to the time when the fish in the sea were the onlyliving creatures. Since then towing has developed into a science with amultitude of devices and systems.

One such device observed by the inventor consisted merely of addingweights to specified locations. Such a system improves to a small degreethe orientation of a towed device. However, many disadvantages emanatefrom such a practice/These include increased towing line tensions,increased snap loads, increased unit weight, poorer handling capabilityand excessive vehicle drag.

SUMMARY OF THE INVENTION Accordingly, it is a general purpose and objectof the present invention to provide a device having improved towingcharacteristics in a liquid medium. It is a further object that thedevice should be'lightweight. Another object is that the device orientsitself upon entering the water and remains oriented in the properdirection regardless of changes in position, velocity and/oracceleration of the vehicle doing the towing. An additional ob je'ct isthat if the main body is cylindrical in shape that the device have aseparation between the center of gravity and center of pressure in airor from A to 1% diameters of the cross-sectional area of the cylindricalbody. Further objects include reduced towing line snap loads, reducedvehicle drag and superior handling capabilities. These and other objectsof the invention and the various features and details of constructionand operation will become apparent from the specification and drawings.

The above objects are obtained by providing a cylindrical main body withfins and auxiliary components that together provide for the separationof the center of pressure and center of gravity and also provide goodflow characteristics for towing through a liquid medium. The size of thefins were determined after extensive experimentation. Portions of thedevice are easily detachable for ease in handling, storage andtransportation and to lessen the chance of damage in handling.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of anembodiment of the present invention; 7

FIG. 2 is a partial side view showing the tail fin assembly of theembodiment of FIG. 1; and

FIG. 3 is a view of a portion of the hollow detachable slotted tubulartail shaft of FIG. 1 with the horizontal and vertical fins removed.

been found to exist is the separation between the center of gravity andthe center of pressure. As the distance between the two is decreased,the time required for change of orientation of the towed device isdecreased. However, this increases'the tow line load. Furthermore, theorientation obtained is less stable. Obviously conditions are reversedwhen the distance between the center of gravity and center of pressureis increased.

It has been determined that in a cylinder an optimum separation betweenthe center of gravity and center of pressure is approximately equal toto 1% diameters of the cylinder for most towing operations.

The following device is useful for obtaining the above characteristicsand has extensive utility for towed transducer systems. In addition, theteachings are also applicable to any other towed system.

Referring now to FIG. 1, there is shown an assembly 10 suitable fortowing. The assembly l0 comprises a main body 11 applicable forenclosing a transducer element or other device that may be insertedwithin. A hemispherical nose .cone 12 is bolted to the forward part ofbody ll 1. The cone 12 is normally made of a relatively heavy materialsuch as steel. Improved towing characteristics such as reductions inturbulence and drag result from the addition of cone 12.

Main body 11 is shown having upper and lower sec tions 14 and 15,respectively. The sections are for the purpose of inserting andwithdrawing equipment. An upper half section of mounting plate 18 isbolted or otherwise affixed to upper section 14. Similarly, a lower halfsection of mounting plate 20 is affixed to lower section 15.

A drop fin assembly 22 is affixed to mounting plate 20. The drop finassembly 22 comprises a drop fin 24, normally made of aluminum orplastic or other lightweight material suitable for use at sea. The dropfin 24 has been found to work best with cylindrical bodies when the dropfin 24 has an area of 20 to 30 percent of the vertical lateralcross-sectional area of the cylindrical body. The drop fin 24 is affixedto the remainder of assembly 22 by means of an aperture in its upperforward comer so that the tin 24 is free to pivot around this aperture,positioning itself in accordance with the position, velocity andacceleration of the main body 1 1.

Drop fin assembly 22 further comprises a rod support bracket 26 affixedto plate 20 by bolts or other suitable means. The bracket 26 furthercomprises a pair of flexible extension arms having a hole in theircenters. A pair of rod supports 32 in the shape of rollers and having anaperture through their centers in an axial direction are located betweenand adjacent to the arms of bracket 26 and drop fin 24. A rod 30 isinserted through bracket 26, rod supports 32 and drop fin 24 to holdassembly 22 in place. The rod 30 may be held in place by cotter pins,bolts, flanges or other suitable means to keep it from slipping out ofassembly 22.

An anti-vortex cone 42 encloses a portion of assembly 22. The drop fin24 extends through a slot 43 in freely.

A hollow tubular detachable slotted tail shaft 34, preferably made ofaluminum or other lightweight material is located aft of main body 11. Avertical fin having sections 36 and 36a, and a horizontal fin havingsections 38 and 38a are inserted in the slotted tail shaft 34 andintermittently welded. Numeral 37 denotes one of a plurality ofintermittent welds shown. The vertical fin 36, 36a and the horizontalfin 38, 38a each have an area 30 to 40 percent of the cross-sectionalarea of body 11.

Shaft 34 is detachably connected to a tubular towing strongback 40 byconnecting means 39 which may comprise nuts and bolts or other suitableattaching means.

The towing strongback 40 connects to and extends aft of main cylindricalbody 11 for insertion into tubular tail shaft 34. The remaining portionof strongback 40 may be any suitable shape and is affixed to body 11.Strongback 40 has apertures 41 for connection to a towing cable (notshown).

Referring now to FIG. 2, there is shown a side view of the drop finassembly 22 portion of FIG. 1. The antivortex cone 42 is shown thatfunctions mainly as a turbulence reducer to give improved performanceduring towing. The cone 42 forms a right circular cone with the diameterto height ratio approximately equal.

FIG. 3 shows a portion of the detachable slotted tubular tail shaft 34with the respective vertical and hori- 'zontal fins 36, 36a and 38, 38aremoved. The slots 44 are shown separated from each other by a rightangle on a plane perpendicular to the shafts 34 axis.

Prior to towing the above assembly a cable is affixed to an aperture 41that is closest to the balance point of the assembly 10 in air. Onentering the water the drop fin 24 orients the assembly 10 for properdirectional attitude.

There has therefore been described an assembly 10 with a basic designfor low drag, quick reaction during towing operations. The device withor without the drop fin assembly has utility as a depressor. A depressortends to orient the towing line in a vertical position bringing thedevice in close proximity to the ship controlling it. Such a device hasquick reaction to the ships movement.

For towed objects having shapes other than a cylinder, an idealseparation of center of gravity from center of pressure may bedetermined from a percentage or ratio of cross-sectional area as in theabove case.

It will be understood that various changes in the details, materials,steps and arrangement of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is: -A .asssmlzlx-ss te ls.forhfi towed i watercomprising;

cal body;

a towing strongback connected to said cylindrical body and extending aftof said cylindrical body;

a tail assembly connected to said towing strongback,

said tail assembly including a vertical fin and a horizontal fin witheach of said vertical fin and horizontal fin having an area equal to 30to 40 percent of the cross-sectional area of said cylindrical body; and

a drop fin assembly connected to said cylindrical body, said drop finassembly including a drop fin having an area of 20 to 30 percent of thevertical lateral cross-sectional area of said cylindrical body fororienting said cylindrical body in water.

2. An assembly suitable for being towed in water according to claim 1wherein said tail assembly further comprises:

a hollow detachable tubular slotted tail shaft detachably coupled tosaid strongback and having slots for insertion of said horizontal andvertical fins.

3. An assembly suitable for being towed in water according to claim 2wherein said drop fin assembly further comprises:

a rod inserted through said drop fin;

a pair of rod supports adjacent to both sides of said drop fin andhaving said rod inserted through said supports in'an axial direction;and

a rod support bracket connected to said cylindrical body and having apair of flexible arms with said arms located exterior to said rodsupports and having said rod inserted therethrough.

4. An assembly suitable for being towed in water acgord'i ng t'oclafiif3 wherein "said" towing strongback includes rrieari s adapted forconnecting atowihg cable.

5. Ari assembly"siiitableforbeing towedin'water according to claim 1further comprising:

an anti-vortex cone connected to the rear of said cylindrical body.

6. An assembly suitable for being towed in water according to claim 5wherein said tail assembly further comprises:

a hollow detachable tubular slotted tail shaft detachably coupled tosaid strongback and having slots for insertion of said horizontal andvertical fins.

7. An assembly suitable for being towed in water according to claim 6wherein said drop fin assembly further comprises:

a rod inserted through said drop fin;

a pair of rod supports adjacent to both sides of said drop fin andhaving said rod inserted through said supports in an axial direction;and

a rod support bracket connected to said cylindrical body and having apair of flexible arms with said arms located exterior to said rodsupports and having said rod inserted therethrough.

8. An assembly suitable for being towed in water according to claim 7wherein said towing strongback includes means adapted for connecting atowing cable.

1. An assembly suitable for being towed in water comprising: a cylindrical body; a hemispherical nose cone connected to said cylindrical body; a towing strongback connected to said cylindrical body and extending aft of said cylindrical body; a tail assembly connected to said towing strongback, said tail assembly including a vertical fin and a horizontal fin with each of said vertical fin and horizontal fin having an area equal to 30 to 40 percent of the cross-sectional area of said cylindrical body; and a drop fin assembly connected to said cylindrical body, said drop fin assembly including a drop fin having an area of 20 to 30 percent of the vertical lateral cross-sectional area of said cylindrical body for orienting said cylindrical body in water.
 2. An assembly suitable for being towed in water according to claim 1 wherein said tail assembly further comprises: a hollow detachable tubular slotted tail shaft detachably coupled to said strongback and having slots for insertion of said horizontal and vertical fins.
 3. An assembly suitable for being towed in water according to claim 2 wherein said drop fin assembly further comprises: a rod inserted through said drop fin; a pair of rod supports adjacent to both sides of said drop fin and having said rod inserted through said supports in an axial direction; and a rod support bracket connected to said cylindrical body and having a pair of flexible arms with said arms located exterior to said rod supports and having said rod inserted therethrough.
 4. An assembly suitable for being towed in water aCcording to claim 3 wherein said towing strongback includes means adapted for connecting a towing cable.
 5. An assembly suitable for being towed in water according to claim 1 further comprising: an anti-vortex cone connected to the rear of said cylindrical body.
 6. An assembly suitable for being towed in water according to claim 5 wherein said tail assembly further comprises: a hollow detachable tubular slotted tail shaft detachably coupled to said strongback and having slots for insertion of said horizontal and vertical fins.
 7. An assembly suitable for being towed in water according to claim 6 wherein said drop fin assembly further comprises: a rod inserted through said drop fin; a pair of rod supports adjacent to both sides of said drop fin and having said rod inserted through said supports in an axial direction; and a rod support bracket connected to said cylindrical body and having a pair of flexible arms with said arms located exterior to said rod supports and having said rod inserted therethrough.
 8. An assembly suitable for being towed in water according to claim 7 wherein said towing strongback includes means adapted for connecting a towing cable. 